Specifications: - Material : Non-woven Cloth,Melt-blown cloth. - Carbon filters size measures approx. 4.72 x 3.15inches. - Five layers of PM2.5 Carbon filtering,Made of activated carbon and non-woven melt-blown filter cloth,effectively keep away from PM2.5 and a range of airborne contaminants. Five Layer Protection: 1st layer of spunbond cloth filters micron-leveldust. 2nd layer filters industrial pollutants, automobile exhaust. 3rd layer of active carbon cloth filters micron-level dust. 4th layer offers filter density for smaller material. 5th layer of spunbond cloth filters out all kinds of harmful substances. Note: 1. When film or sticky sediment stains emerge, please replace the filter. 2. Filter insert can not be cleaned and should be replaced everyday for getting best protection.